The standard sizes of bi-pin, two-, four- and eight-foot length fluorescent lamps have heated filaments at one or both ends and hence are thermionic. That is, they require heated filaments for operation at relatively high starting voltages. Heated filaments shorten the life of the lamp leading to relamping programs at large installations such as schools, warehouses, factories, large stores, office complexes, etc. These relamping programs periodically replace the fluorescent lamps to avoid decreasing luminous efficiencies because of darkened ends due to sputtering at the filaments, the down time caused by the sporadic failure of and unexpected lamp failures, etc. Moreover, heated filaments radiate heat and cause added air conditioning or cooling expenses in terms of electrical energy usages.
The three major causes of lamp failure are:
1. Filament open (non-functional).
2. Intrusion of metal vapors (from the evaporation of the hot filaments) in the mercury vapor inside the lamp, causing loss of light output, due to diluted concentration of mercury, and eventually flicker.
3. Glass breakage:
Eliminating the first two major causes (eliminating the filament), the tube life could be extended beyond the present use, doubling, tripling, quadrupling or beyond the useful life of the lamp, the intrusion of mercury into the environment due to lamp disposal, will be cut by 50%, 66%, 75% or beyond per year. The annual amount of mercury intrusion on the environment is in excess of 15 billion milligrams of mercury per year.
Ref: 500,000,000 fluorescent lamps disposed yearly at 30 mg of Hg per lamp.
The above is an ever increasing intrusion due to the increasing use of fluorescent lighting.
The object of the present invention is to provide non-thermionic lamps and driver systems which avoid the above-noted problems in the art.
Moreover, prior art fluorescent lamps have a relatively high mercury content which causes disposal/recycling problems for landfills, etc. Another objective of the invention is to provide a fluorescent lamp with substantial increase in lamp life due to the avoidance of filament failure (major cause of relamp/replace) as well as contamination of the gas by evaporating hot filaments. Due to the preservation of the integrity of the gas, lower mercury content in these lamps is contemplated. Even if the mercury content is the same, due to the long lamp life, replacement is significantly reduced, thereby reducing mercury disposal problems.
According to the invention, filamentless electrodes are mounted at the ends of standard lengths fluorescent lighting tube (two, four and eight feet) and have standard, conventional bi-pin mounting arrangement at each end so that conventional fluorescent tube sockets can be used. A low voltage square wave alternating current driver circuit having a frequency in the range of about 75 kHz to about 3.9 MHz is connected to the electrodes to thereby energize the lamp. In a preferred embodiment, a pair of lamps are connected in series across a low voltage square wave alternating current source having a frequency of about 100 kHz.
In my patent application Ser. No. 08/942,670 filed Oct. 2, 1997, I disclose a novel non-thermionic fluorescent lighting system using square wave alternating current drivers.